Cutting sweet potatoes with some regular russets gives the mash added body, and makes the dish all the more savory. Try adding some spices to the onion topping if you're going a non-traditional route. —PhoebeLapine
1 pound russet potatoes, peeled and diced
1 pound sweet potatoes, peeled and diced
1 large sweet vidalia or Spanish onion, halved and thinly sliced
In a large saucepan, cover the potatoes with cold water. Bring to a boil over high heat. Simmer until the potatoes are fork tender, about 10 to 15 minutes. Drain and return to the pot. Using a masher or fork, crush the potatoes until no chunks remain. Whisk in the butter and season to taste with the cayenne, nutmeg, and salt.
Meanwhile, heat the oil in a large cast iron skillet. Saute the onions over medium-high heat until soft and beginning to brown, about 8 minutes. Reduce the heat to medium-low and continue to cook the onions, stirring occasionally, until very browned and caramelized, about 30 minutes. This is a low and slow process and shouldn't be rushed - your onions will be about 1/4 of the size they were at the beginning. Season to taste with salt and pepper.
Transfer the potatoes to a casserole dish and top with the caramelized onions. Can be make 2 days ahead and reheated in a 350 degree oven.
Phoebe is a writer, gluten-free chef, culinary instructor, award-winning blogger, and author of The Wellness Project. You can find her healthy comfort food and gluten-free finds on www.FeedMePhoebe.com